The substance which is the subject of the invention is an analogue of a known therapeutic, namely sulfasalazine (i.e. 5-[4-(2-pyridysulfamoyl) phenylazo] salicylic acid) discovered in 1942 (Acta Medica Scandinavica 60, 1942, p. 577-598, N. Schwartz) and used in the therapy of progressive polyarthritis and ulcerative colitis. Sulf asalazine also influences various steps in the metabolism of arachidonic acid and has immunomodulating properties (J. Clin. Invest. 69, 1982, p. 494, W. R. Stenson). A shortcoming of this drug is its low biological availability and some unfavorable side effects. Therefore a series of analogues of sulfasalazine was synthesized with the aim to finding a substance of more favorable therapeutic and pharmacokinetic properties, especially a higher biological availability.